The Stovebolt Site Forums The Shop Area Interiors 1949 GMC Speedometer

Looking for advice here. My speedometer had been bouncing around and getting louder for some time (drove infrequently). I've replaced the cable and ensured it was lubed. I've disassembled the speedometer and lubed the gears and the "cup" in the rear with sewing machine oil, and it seems to run very smoothly when out of the truck. Running it with a drill or my fingers makes no odd sounds.

After the new cable, lubed speedometer, and some tinkering with tightness on the cable, it is at least holding pretty steady. It seems accurate up until about 10 mph, but seems to hang up around 10 mph just long enough to be about 7 mph slow, then continues to rise as speed increases. There is an audible noise coming from behind the dash too when it's all hooked up.

Does anyone have any ideas about what this might be caused by?

Check your PM..

I have this same problem with the needle going every which way and the rattling noise in the dash. I have a TH350 trans...any help or ideas?

Something like that happened with my speedometer when I installed a new cable(20 years ago). I loosened the cable on the speedometer and the problem went away. I didn't like that the cable was not screwed tightly to the speedometer, but it fixed the problem. Recently, I rebuilt my speedometer and found a couple issues that you could check. If you want to open up the speedometer, make sure the speedcup is not binding. You can rotate the speedcup and the spring should return it to rest position. The speedcup assembly has 4 screws, if there is a bind, you can loosen the screws and might be able to shift the assembly so the speedcup moves freely, and then tighten the screws. The steel spindle is soldered to the aluminum speedcup, that can break. Make sure the spindle is not independent of the speedcup, it can be bad but have enough friction to appear good.